Oil performs critical roles in an engine including lubrication of rapidly moving parts and providing fluidic support to the crankshaft journal bearing. Oil used in an engine is exposed to high temperatures and adverse conditions over durations of engine operation. Oil quality degrades over time and usage, and the oil must periodically be replaced. Two primary modes of oil quality degradation include oxidation and contamination.
Oxidation is a predictable outcome of oil use within a combustion engine. One known method to protect against oil oxidation within an engine is to estimate the oil quality over time and prescribe oil changes after a given time elapsed interval or distance traveled interval. However, estimating optimal intervals between oil changes is an imprecise method to estimate a required oil change. Oxidation does not occur at a constant rate and may be affected by many factors, including the operating temperature for the oil, with higher temperatures causing more rapid oxidation. An optimal interval between oil changes for one vehicle may be very different from the optimal interval for another vehicle based on these factors. Another known method to protect against oil oxidation within an engine is to perform chemical analyses of the oil. Oxidation produces chemical by-products and may be quantified by analyzing oil samples. These chemical analyses may be utilized to improve the accuracy of oil oxidation estimates, but these analyses are difficult to perform, and must either be performed outside the vehicle in a repair shop or require expensive additional equipment to perform on-board the vehicle.
Contamination is another mode of oil quality degradation. Many sources of oil contamination exist, but water and fuel are the most typical contaminants in oil. One known exacerbating circumstance to oil contamination is short trip usage. Both water and fuel have lower boiling points than oil and will evaporate out of an oil-contaminant mixture when the oil gets up to certain operating temperatures. Vehicles are designed such that normal operating temperatures will purge water and fuel from the oil. However, if a vehicle is used only on short trips where the engine is not permitted to reach normal operating temperatures, the water and fuel contaminants accumulate and remain in the oil. These contaminants interfere with the operation of the oil throughout the engine and, if present in sufficient quantities, cause engine damage.